Transformer connection for hot cathode rectifiers



Dec. 13, 1927.

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Patented Dec. 13, 1927.

UNITED STATES PATENT oFFic-E.

EDGAR W. BREISCH, OF EDGEWOOD, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

TRANSFORMER CONNECTION FOR HOT CATHODE RECTII'IEBB.

Application filed November This invention relates to the transformer conngctions for hot cathode rectifiers, vparticularly of the type utilizing a single halfwave'tof an alternating current.

Inthe construction of transformers for supplying rectifiers of the battery-charging type, it is necessary to provide for considerable leakage. in the transformer, in order that the direct current voltage will fall off very materially with an increase in current above a predetermined value. J 1

' Heretofore, ithas been customary to place a small coil for energizing, the filament of the rectifier bulb on one leg of the transformer, the transformer being constructed with the load circuit either entirely on that leg or on the other leg. vAssume,'for example, an auto transformer comprising two coils, one on each leg of a core, said coils be.-

ing connected in series across a hundred volt line. The normal voltage ateach of the coils is then volts.

When a rectifier is connected across one of these coils and a load current is drawn, the voltage will drop to,say, twenty-five volts on that coil, while owing tomagnetic leakage around said legs the voltage on the other coil will rise to seventy-five.- If, now, the filament coil is placed on the seventy-five volt leg, the filament will receive an abnormal current and tend to burn out.

If, however, the filament coil is placed upon the twenty-five volt leg, the temperature of the filament will not be. hot enough, thus approaching the condition of the nonexcited filament. Under these conditions, it has been found that the rectified current will continue to fiow, even after the filament heating current. is entirely interrupted, a small portion of the filament being heated by the rectified current to' a temperature high enough to cause this hot portion to continue to give off electrons. As a rule, the filament breaks at the place where this hot spotoncurs, after operating under these conditions but a short time. To'obviate these" difficulties it has been necessary, heretofore, to resort to much larger filaments than would otherwise be necessary.

= 12 complished by'dividing the filament winding,

It is the object of my invention, therefore,

20, 1920. Serial N0. 425,497.

placing part on one leg and part on the other leg of the transformer, whereby the decrease in the flux of the one leg will be compensated for by the increase in the other leg.

Referring to the drawings, wherein 9. diagrammatic representation of my invention is shown, I provide an auto-transformer I havmg coils 2 and 3 connected in series across an alternating current sup 1y line indicated by a plug connector 3a. The midpoint 4.. of the auto-transformer is connected to the anode 5 of a bulb 6, said bulb having a filamentary cathode 7 which is adapted to be connected to one terminal of a battery. The other terminal of the battery is connected to the terminal 8 of coil 3. The current for exciting the filament is obtained from two coils 9 and 10, placed on the respective legs ,of the transformer coil, whereby a constant voltage will be obtained, as hereinbefore ex-- plained. It is apparent that taps may be provided in either coil 2 or coil 3 for obtaining different batter voltages and also that different degrees 0 regulation mayube obtained by different numbers of turns of the coils 9 and 10 on the respective legs of the transformer. V

The operation of my device is as follows:

The load current is obtained from a transformer winding placed either entirely, or mostly, upon one leg of the transformer coil. The drawing shows the load winding 3 as being placed entirely u on one leg. Under these circumstances, tliie transformer has very poor regulation. That is, when the load comes on, the flux and hence the voltage in coil 3 drops very materially, while the voltage on coil 2 increases correspondingly.

- The filament coils'9 and 10 are so proportioned, as to the number of turns in each, that the total electromotive force applied to the filament remains substantially cohstant.

While I have ilhlstrated my invention in its preferred form, it is to be understood that it is susceptible of various modifications by.

'those skilled in the art and that the claims are to be construed to cover all such modifi- Y cations except where limited by the state of the art.

I claim as my invention 1. The combination with a transformer core having: two legs, of coils on each leg, means for supplying power to coils on both legs, means for withdrawing the main part of'the load current exclusively from turns mainly on. one leg, and means for supplying from said transformer an auxiliary current from turns on both legs.

2. The combination with a transformer core comprisin two serially connected magnetizable portions arranged to rovide a leakage path therebetween, of coi s on each portion, a primary circuitnonnected across coils on both portions, a secondary circuit 10 connected across turns predominantly on onguportion whereby relatively poor voltage re leakage path, and an auxiliary circuit including coils on both portions whereby rela-' tively good regulation is obtained.

3. T e combination with a rectifying device having a heated filament, of a transformer comprising a core having two legs and a C01]. on each leg, a supply c1rcu1t connected across serially connected turns on both legs, a load circuit including said rectifying device and connected across turns on one leg, and a filament-energizing circuit connected across turns on both 4. The combination with arectifylng device having a heated filament, of a trans Y, provide a 1 on both port-ions as to obtain relatively good voltage regulation.

ation is obtained by reason of said- 5. The combination of an auto-transformer having two legs and coils upon each leg, aload circuit energized mainly by one of the coils upon one leg of said transformer, an auxiliary coil on each leg of said transformer, and a load circuit including said auxiliary coils connected in series.

6. The, combination with an auto-transformer comprising a core having two legs and a coil upon each leg, of a main loail' circuit connected across "turns mainly upon a single leg, and an auxiliary load circuit connected across coils upon both legs.

7. In a battery-charging system, the com bination with an auto-transformer having two legs and having a coil disposed upon each leg, of a battery circuit including a filamentary bulb, said battery circuit being energized from turns disposed upon a single leg ofsaid transformer, and an auxiliary coil on each leg of said transformer, said auxiliary coils being connected in series with each other to energize the filament of said bulb. o

81- A transformer; having two legs and a coil on each leg, 'means for energizing said transformer including turns equally distributed on both legs, means for supplying from said transformer a load current of relatively poor regulation, said load current being drawn from turns mainlyon one leg, and means for supplying from said transformer an auxiliary current of good regulation, said last-mentioned means including turns on both of said legs.

In testimony whereof, I have hereunto subscribed my name this 4th day of November, 1920.

EDGAR w. BREISCH. 

